Breast cancer genetic risks not affected by lifestyle factors

Breast cancer genetic risks not affected by lifestyle factors

Women's risk of developing breast cancer due to common genetic differences is not affected by lifestyle factors such as weight, diet, alcohol, hormone replacement therapy (HRT), having children and breastfeeding, concluded UK researchers.

The study, led by a team at the University of Oxford, is published 2 June as an early online publication in the The Lancet.

Lead author Dr Ruth Travis, an epidemiologist who specializes in investigating the genetic, hormonal and lifestyle determinants of cancer, told the press that we know lifestyle and genetic factors affect breast cancer risk, but this research shows that lifestyle factors do not influence the genetic risks, their influence is independent of one another:

"We looked at whether lifestyle factors for breast cancer, such as use of HRT, alcohol consumption and reproductive history, influence the genetic risks: and the answer is that they do not," said Travis, according to a Reuters report.

Travis and colleagues found that for most women, modifiable lifestyle factors influence breast cancer risk more than inherited genes.

Co-author Dr Jane Green, also an epidemiologist at Oxford with interests in how environment affects cancer risk, said:

"Genes account for only a small proportion of breast cancers, and for most women the main risk factors remain the lifestyle factors such as child bearing, use of HRT, obesity and alcohol consumption."

She said the good news is that some of these lifestyle factors are modifiable, so women can change their risk of breast cancer by changing their behaviour.

For the large prospective UK-wide study, Travis, Green and colleagues compared 7,160 women with breast cancer with 10,196 who did not have the disease. They examined the effect of 12 polymorphisms (genetic variations) and ten established lifestyle factors, such as age when they had their first baby, breastfeeding, age at menopause, use of HRT, BMI, height and consumption of alcohol.

The found no evidence that any of the lifestyle and genetic factors combined to raise the risk further. They wrote that:

"After allowance for multiple testing none of the 120 comparisons yielded significant evidence of a gene-environment interaction."

They wrote this was in contrast with previous suggestions that HRT use influenced genetic risk, "either overall or for oestrogen-receptor-positive disease".

Talking about the findings in a telephone interview, Travis said these results are reassuring because no matter what risks you inherit through your genes, the effect of things you can do something about, such as "maintaining a healthy weight, limiting alcohol intake and being careful about HRT are still really important for reducing breast cancer risk," reported Reuters.

"Gene-environment interactions in 7610 women with breast cancer: prospective evidence from the Million Women Study."

Ruth C Travis, Gillian K Reeves, Jane Green, Diana Bull, Sarah J Tipper, Krys Baker, Valerie Beral, Richard Peto, John Bell, Diana Zelenika, Mark Lathrop, for the Million Women Study Collaborators.

The Lancet, Early Online Publication, 2 June 2010


Additional source: Reuters.

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Section Issues On Medicine: Women health